The present invention relates to packaging and mounting beam-lead diodes in a stripline, coaxial or waveguide assembly.
Beam-lead technology is ideally suited to the production of diodes which must operate at high frequencies with low loss due to parasitic elements associated with the elements of the device. Beam-lead diodes also provide excellent mechanical reliability and can be protected by an appropriate encapsulant which adds negligibly to device parasitics without degrading RF performance. Beam-lead devices are easily adapted to mounting in microwave-integrated circuitry but difficult to adapt to other environments. This occurs because the diode is normally bonded in place and field replacement is difficult if not impossible.
Semiconductor chip diodes have been successfully packaged in various configurations. Usually these packages contain a spring-loaded pin or a fine gold wire to contact the enclosed semiconductor chip. The pin and the wire contribute a parasitic inductance in series with the semiconductor. Parasitic capacitance contributed by the cross-sectional area of the pin and end contacts of the package in conjunction with the parasitic inductance create spurious resonances that make satisfactory operation above 30 GHz nearly impossible. For more information concerning parasitic elements associated with conventional packaged and mounted diodes the article "The Packaged and Mounted Diode as a Microwave Circuit" by W. J. Getsinger, IEEE Transactions on Microwave Theory and Techniques, vol. MTT-14, No. 2, February, 1966, pp 58-69, which is incorporated herein by reference.
U.S. Pat. No. 3,974,518 discloses a package for microwave diodes wherein the semiconductor chip is mounted upon a diamond member embedded in a copper base member so that the diamond mounting surface and the copper base member surface are coplanar. A quartz insulator surrounds the chip and reduces parasitic capacitances to an extent. However, the diode is suitable for X-band (up to 8-12.5 GHz) operation only.
What is needed then is a packaging and mounting method apparatus and method for removably mounting a beam-lead diode in a coaxial, stripline or waveguide assembly that does not appreciably degrade device performance in the microwave and millimeter frequency ranges.